1. Om registrene

Posisjon  1

The quality and use of two health registries in Russia

Arild Vaktskjold, department of epidemiology and biostatistics, , Institutt of Community Medicine. Doctoral work submitted 2005.

Background
In the late 1990s, a birth registry (KBR) was set up for the borough of Mončegorsk in the Kola Peninsula and a cancer registry (AKR) for Arkhangelskaja Oblast (AO), both located in north-west Russia. The work in this thesis involves an assessment of the quality and content of the two registries, including an estimation of the site- and gender-specific cancer incidence in AO. The work also involves the use of the birth registry to study the effect of maternal exposure to nickel at the workplace on the risk of being born with a birth defect. This was one of the objectives behind the construction of the birth registry. Genital malformations were chosen as the outcome in this first of such studies based on the KBR.

Important source of data
The KBR has proved itself to be a comprehensive source of data concerning the mother, pregnancy and newborn. It contains data about pregnancy outcomes after 28 weeks of gestation for 24 534 births in Mončegorsk in the period March 1973-2001, including the most pertinent known factors that may influence the outcome. More than 17 000 different women are registered and very few births are missing. The registered data about maternal occupation, employer, infections, previous abortions and disease history make the KBR and its potential relatively unique. The availability of data about the women’s employer and occupation made it practicable to assign data in the registry about nickel exposure. Some registered data items are not complete enough to be useful, but the KBR contains sufficient data to investigate the incidence of different maternal and newborn health conditions, and the etiological effect of maternal workplace-exposure to water-soluble nickel. The statistical analyses revealed that perinatal mortality has decreased over the years since 1973, and that twenty-two percent of the newborns were delivered by women employed within the complex of the local nickel refinery in early pregnancy. No association was found between the maternal nickel exposure and the risk of being born with a genital malformation.

Accessabillity
The standardised setting of health, pregnancy, delivery and newborn care, as well as data recording, makes the KBR advantageous for research purposes. The easy accessible insight to the recording and care such a setting provides, makes it more feasible to detect, and perhaps overcome, systematic errors. However, the number of records is not yet large enough to present trends of rare outcomes and health conditions in Mončegorsk, or to do etiological research concerning such factors.

under-estimations of cancer
The existing cancer-reporting system in AO facilitated the setting-up a systematic population-based registry. Almost 35 000 new cases of cancer were reported in the period 1993-2001, and the information that is considered important in a cancer registry was available in the patient reports submitted to the oncological hospital. The high internal consistency of the registered data indicated that there were few data-entry and transcription errors, or that the visual control routines of the registered data were good. However, randomly extracted journals in two regional hospitals revealed that 6.0 percent (+/- 4.7%) of the cases were not registered in the AKR. All of the missing were from the same clinic. This finding suggests that it would have been advantageous to control additional regional hospitals. Furthermore, sailors, railway and shipyard workers had their own health care system, so there is also some uncertainty to what extent cancer cases from these groups were reported to the oncological hospital. The 2002-census revealed that the actual population in AO was about six percent lower than the official population figures, which indicates that the population figures used to estimate the cancer incidence were inflated for the last years of the study period. These findings indicate that the cancer incidence rates reported herein are underestimations, mainly among men. Still, the estimated cancer incidence of all major cancer sites was higher among men, which suggests that the overall underestimations were relatively low.

Gender differences
Our findings indicate that the incidence of melanoma of the skin and cancer of the stomach, larynx, liver, pancreas, prostate, colon, and bladder is quite different in the male population in AO than in Norway. Among women, most major cancer types, except stomach, appear to be relatively low in the AO population. The reported incidence rates in AO contribute to the discussion and generation of hypotheses concerning the role of different lifestyle and environmental factors in the aetiology of different cancer types. Thus, the AKR provides useful data and interesting insight into cancer incidence in a northern Russian population.


List of papers
This thesis is based on the following four papers.
I. Vaktskjold A, Talykova L, Chashchin V, Nieboer E, Odland JØ. The Kola Birth Registry and perinatal mortality in Mončegorsk, Russia. Acta Obstet Gynecol Scand 2004 Jan;83(1):58-69
II. Vaktskjold A, Paulsen EA, Talykova L, Nieboer E, Odland JØ. The prevalence of selected pregnancy outcome risk factors in the life-style and medical history of the delivering population in north-western Russia. Int J Circumpolar Health 2004 Mar;63(1):39-60
III. Vaktskjold A, Talykova LV, Chashchin VP, Nieboer E, Thomassen Y, Odland JØ. Genital malformations in newborns of female nickel-refinery workers. Scand J Work Environ Health, in press.
IV. Vaktskjold A, Lebedintseva JA, Korotov DS, Tkatsjov AV, Podjakova TS, Lund E. Cancer incidence in Arkhangelskaja Oblast in northwestern Russia. The Arkhangelsk Cancer Registry. BMC Cancer 2005; 5:82.